Update Firefox self hosted manifest to version v1.22.0

Author: github-actions[bot]

.ff_updates.json

@@ -2,6 +2,10 @@
   "addons": {
     "betteriutrcc@simon511000.fr": {
       "updates": [
+        {
+          "version": "1.22.0",
+          "update_link": "https://github.com/PaulBayfield/Better-IUT-RCC/releases/download/v1.22.0/Better-IUT-RCC-v1.22.0.xpi"
+        },
         {
           "version": "1.21.1",
           "update_link": "https://github.com/PaulBayfield/Better-IUT-RCC/releases/download/v1.21.1/Better-IUT-RCC-v1.21.1.xpi"